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Curated by: Qiskit (180 videos)
When Being Sloppy Helps: Non-Hermiticity and Anomalous Relaxation | Qiskit Quantum Seminar Hosted by Zlatko Minev, PhD. Please feel free to join our public Slack workspace to continue the conversation: http://qisk.it/join-slack Abstract: Quantum mechanics is ruled by Hermitian generators inducing unitary propagation, nevertheless, when tracing out some degrees of freedom one can end up with non-Hermitian operators. An example is entanglement or out-of-time-ordered correlation functions in random circuits, where the relaxation dynamics is described by a non-Hermitian Markovian matrix with a finite gap. Naturally one would expect that the relaxation, i.e., the rate of generating entanglement, will be given by this finite spectral gap. However, this is not the case. Rather, in the thermodynamic limit the rate is given by a phantom eigenvalue -- an "eigenvalue" that is not in the spectrum. Resolution of this puzzle will lead to a pseudospectrum and a realization that when dealing with non-Hermitian matrices being exact can actually be wrong, while being slightly wrong is correct. Bio: Marko Znidaric is a professor of physics at University of Ljubljana, Slovenia. After obtaining Ph.D. in 2004 on stability of quantum dynamics and Loschmidt echo he became interested in quantum information and more broadly in the physics of quantum many-body systems. He studied transport in spin chains, Lindblad master equations, and more recently came across interesting effects of non Hermiticity that few years ago he though is just obscure mathematics.